This invention relates to the authentication of visual images such as are produced by a video camera or the like, and more particularly to a method of authentication employing algorithms to encode information by which the image can be authenticated.
There are a variety of situations in which it is important to know that a visual image such as an image transmitted from one location to another, or a stored image which is to be used at a later time is provided or maintained in the exact form in which it was produced. In the medical field, for example, it is now commonplace to transmit a picture (a visual image) of a patient from one site (a local hospital, for example) to another (the location of a specialist). The image may be an x-ray, CAT scan image, or other image of the patient. Because the image may be used in making a diagnosis, describing a medication or course of treatment, or viewed by a specialist while surgery is being performed, any inaccuracies in the received image can potentially have serious consequences. And, it is known that transmission errors due to noise on the transmission line, temporary disruptions, etc. do occur.
As a further example, many police interrogation rooms are equipped with video equipment so the police examination of a suspect can be recorded. The resulting record can then be used for evidentiary purposes, as well as to defend the police against charges by a suspect that he was mistreated or that a confession was forced from him.
In security systems, to use another example, a video system may capture the image of an intruder during an unauthorized entry. The image therefore can become part of the evidence which is used to prosecute a suspect. To use the image as evidence against the suspect at trial, it is necessary to maintain the image in its original form and do so in a way that the custodian of the evidence can clearly demonstrate to a court that the image has not been tampered with. It is well known that technology exists by which images can be modified. Such technology can be used to alter the image in such a way that its evidentiary value is destroyed. It is thus important to provide a foolproof method by which tampering can be prevented, or if tampering occurs, it is readily discernible.